Investigation of l/f Noise Mechanisms in Midwave Infrared HgCdTe Gated Photodiodes

In this work, gated midwave infrared (MWIR) Hgl,Cd., Te photodiodes are used to investigate the physical origin of 1/f noise generation. Gated photodiodes were fabricated on liquid-phase epitaxy p-type HgCdTe MWIR material with a vacancy-doped concentration of 1.6 x 10(16) cm(-3) and x = 0.31. CdTe was thermally deposited and used as both a passivant and a mask for the plasmabased type conversion, and ZnS was used as an insulator. Fabricated devices show a R(0)A of 1-5 x 104 Omega cm(2) with zero gate bias. Application of 2 V to the gate improves the R(0)A by more than two orders of magnitude to 6.0 x 10(6) Omega cm(2), which corresponds to the p-type surface being at transition between depletion and weak inversion. Trap-assisted tunneling (TAT) current was observed at negative gate biases and reverse junction biases. For gate biases greater than 3 V, a field-induced junction breakdown was observed. An I-n = a I(beta)f(-0.5) trend was observed above 200 pA reverse bias dark current, with alpha = 3.5 x 10(-5) and P = 0.82, which corresponds to the TAT dominated region. Below 200 pA, junction generation-recombination (GR) current starts to dominate and this previously mentioned trend is no longer observed. Junction GR current was not seen to be correlated with 1/f noise in these photodiodes.